Variable resistance device



June 14, 1955 s, GREENE 2,710,898 I VARIABLE RESISTANCE DEVICE FiledOct. 15, 1952 as 26 so 32 4 INVENTOR.

s/0/vEV R. GREENE (Eh 4M,

ATTORNEY United States Patent VARIABLE RESISTANCE DEVICE Sidney R.Greene, New Haven, Conn., assignor to Bendix Aviation Corporation,Teterboro, N. J., a corporation of Delaware Application October 15,1952, Serial No. 314,921

7 Claims. (Cl. 201-52) The present invention relates to control devicesfor electrical circuits and more particularly to a variable resistancedevice for making fine and accurate resistance adjustments.

An object of the present invention is to provide a novel variableresistance device of few and simple parts for making fine and accurateresistance adjustments.

The present invention, therefore, contemplates a novel and simplevariabie resistance device which comprises a resistor element in theform of a coil spring and a member adapted to travel between theconvolutions of the spring. The member is interposed between a pair ofadjacent convolutions and is urged in a direction to compress a portionof the spring so as to eifect engagement of the convolutions of saidportions. Means are provided for effecting relative movement between thespring and the member, as to effect an increase or a decrease in thenumber of convolutions engaged, to vary the effective resistance of thedevice.

The above and other objects and advantages of the present invention willappear more fully hereinafter from a consideration of the detaileddescription which follows, taken together with the accompanying drawingwherein one embodiment of the invention is illustrated.

In the drawing:

Figure 1 is a view, in section, of one form of a variable resistancedevice embodying the present invention; and

Figure 2 is an exaggerated view of a disc-like member used with thevariable resistance device of Figure 1.

Referring now to the drawing for a more detailed description of thepresent invention and more particularly to Figure 1 wherein oneembodiment hereof is clearly illustrated, a variable resistance device,generally designated by the numeral 11, comprises a cylindricalcontainer 12 of suitable insulating material provided with spaced endwalls 14 and 15. End wall 15 may be cemented, for example, to

container 12, or secured thereto in any suitable manner, to

close-off the container. Disposed within container 12 is a resistorelement, or a resistance wire, in the form of a coil spring 17 which maybe helical, as shown in Figure l. The ends of spring 17 protrude throughopenings 18 formed in end walls 14 and and portions of the ends arefixedly secured to the walls, in any suitable manner,

such as for example, by adhesive material. The ends of spring 17 may beconnected to a pair of conductors (not shown) to connect device 11 in anelectrical circuit.

Projecting through an aperture formed in end wall 15, and extendingaxially of spring 17, is a shaft 19 of an adjusting member 21. Member 21has a slotted head 23 which is engageable by a suitable tool to providerotation of the shaft. Shaft 19 has a rectangular-shape portion 24 whichcooperates with a rectangular slot 25 (Figure 2) for rotation with theshaft. Portion 24 is peened to prevent separation of member 26 and theshaft, but the dimensions of slot 25 and portion 24 are such that thedisc-like member may have a wobbling motion, in addition to beingrotatable with the shaft.

Disc-like member 26 is interposed between a pair of adjacentconvolutions of spring 17 and has a pair of diametrically opposed cars30 (Figure 2) which engage the convolutions. It may be understood thatthe pitch of spring 17 provides for threading of disc-like member 26between the convolutions of the spring, upon rotation of adjustingmember 21, as to efiect movement of member 26 axially of the spring.Arranged on shaft 19 and extending axially of spring 17 is a compressionspring 32 which engages disc-like member 26 and urges the latter in adirection to provide compression of part of spring 17 (Figure 1),whereby the adjacent convolutions thereof engage each other and thussubstantially short circuit each other. The force exerted by spring 32is greater than the force offered by spring 17, and since the ends ofthe latter spring are fixed, the other part of the spring is expanded,whereby the convolutions thereof are disengaged.

To vary the effective resistance of device 11, adjusting member 21 isrotated in one direction or the other, so that the cars 30 travelbetween the convolutions of the spring to decrease, or increase, thenumber of convolutions engaged, or disengaged. It is apparent that theeffective resistance of the device is a function of the number ofconvolutions engaged, or disengaged, so that an increase in the numberof convolutions engaged, provides for decreased resistance while adecrease in the number of convolutions engaged, provides for increasedresistance.

It may now be understood that the present invention provides a novel andeffective variable resistance device of relatively few parts for makingfine and accurate resistance adjustments. By providing a rotatablespringpressed disc-like member between a pair of adjacent convolutionsof a resistance coil spring, the number of convolutions engaged, ordisengaged, may be varied without the use of threaded parts, and thelike.

Although one embodiment of the invention has been illustrated anddescribed in detail it is to be expressly understood that the inventionis not limited thereto. Various changes can be made in the design andarrangement of the parts without departing from the spirit and scope ofthe invention as the same will now be understood by those skilled in theart.

I claim:

1. A variable resistance device of the class described i comprising aresistor element in the form of a coil spring having a plurality ofconvolutions, a member interposed between a pair of adjacentconvolutions of said spring, said member engaging at least oneconvolution of said pair and providing compression of a part of saidspring whereby the convolutions thereof engage each other and providingexpansion of the other part of said spring whereby the convolutionsthereof are disengaged, and means providing relative movement betweensaid spring and said member to vary the number of convolutions engaged,or disengaged, to thereby vary the effective resistance of the device.

2. A variable resistance device of the class described comprising aresistor element in the form of a helical spring, a disc-like memberinterposed between a pair of adjacent convolutions of said spring andhaving extending portions thereof engaging at least one convolution ofsaid pair, spring means urging said disc-like member in a direction tocompress a portion of said spring whereby the convolutions thereof areengaged, and means mounting said disc-like member and operable fordisplacing formed in a disc-like member 26, to support the latter thelatter axially of said spring to vary the number of convolutionsengaged.

3. A variable resistance device of the class described comprising aresistor element in the form of a helical spring having a series ofnormally spaced convolutions, a rotatable shaft extending axially ofsaid spring, a disclike member mounted on said shaft for rotatablemovement therewith and interposed between a pair of adjacentconvolutions of said spring, said disc-like member having a pair ofextending portions engaging at least one convolution of said pair, andresilient means urging said disc-like member to compress a part of saidspring whereby the convolutions thereof are engaged and to expand theother part of said spring whereby the convolutions thereof aredisengaged, said shaft being rotatable in either direction to providetravel of said disc-like member between the convolutions of said springto decrease or increase the number of convolutions engaged, ordisengaged, depending upon the direction of rotation of said shaft, tovary the effective resistance of the device.

4-. A variable resistance device of the class described comprising ahollow cylindrical container of insulating material having end walls, aresistor element in the form of a helical spring within the containerand having its ends fixed to said end walls, a rotatable shaft extendingaxially of said helical spring, a disc-like member mounted on said shaftfor rotation therewith and interposed between a pair of adjacentconvolutions of said helical spring, a spring operatively connected withsaid disc-like member and urging it in a direction to compress a part ofsaid helical spring whereby the convolutions thereof are engaged and toprovide expansion of the other part of said helical spring whereby theconvolutions thereof are disengaged, said shaft being rotatable toprovide travel of said disc-like member between the convolutions of saidhelical spring to decrease or increase the number of convolutionsengaged or disengaged to vary the effective resistance of said device.

5. A variable electrical impedance device comprising an electricalimpedance element in the form of a coil spring having a plurality ofconvolutions, means including a member interposed between a pair ofadjacent convolutions of said spring and in engagement with aconvolution of said pair for providing compression of a part of saidspring whereby the adjacent convolutions thereof engage each othersubstantially to short circuit each other and for providing expansion ofthe other part of said spring whereby the convolutions thereof aredisengaged, and means for moving said member between the convolutions ofsaid spring and along the axis thereof to vary the number ofconvolutions engaged, or disengaged, and thereby vary the effectiveimpedance of the device.

6. In a variable electrical impedance device, a coil spring having aplurality of turns of electrically conductive material distributed alongthe axis of the spring, a member disposed between a pair of adjacentturns of said spring and in engagement with the spring so that someturns are compressed with the adjacent turns of the compressed turnsengaging each other and substantially short-circuiting each other andother turns of said spring uncompressed with the uncompressed turns outof engagement with each other, and means for threading said memberbetween the turns of said spring in one direction along said axis sothat for predetermined increasing axial positions of said member in saidone direction an increasingly fewer number of turns are compressed andshort-circuited and for threading said member between the turns of saidspring in the opposite direction along said axis so that for increasingaxial positions of said member in said opposite direction anincreasingly larger number of turns are compressed and short-circuited.

7. A variable electrical impedance device comprising an impedanceelement in the form of a coil spring having a plurality of convolutions,a member interposed between a pair of adjacent convolutions of thespring and engaging at least one convolution of said pair, means urgingsaid member in one direction to compress a part of said spring wherebythe adjacent convolutions there of engage each other substantially toshort circuit each other and to provide expansion of the other part ofsaid spring whereby the convolutions thereof are disengaged, and meansfor operating said member for travel between the convolutions of saidspring in said one direction to compress additional convolutions of thespring so that additional convolutions engage each other to decrease theefit'ective impedance of said device and in the opposite direction toprovide a reduction in the number of convolutions which engage eachother to increase the effective impedance of the device.

References Cited in the file of this patent UNITED STATES PATENTS435,985 Thone Sept. 9, 1890 FOREIGN PATENTS 265,676 Great Britain Feb.9, 1927

